This invention relates to organophotoreceptors suitable for use in electrophotography and, more specifically, to flexible organophotoreceptors having an improved charge transport compound comprising a hydrazone group.
In electrophotography, an organophotoreceptor in the form of a plate, disk, sheet, belt, drum or the like having an electrically insulating photoconductive element on an electrically conductive substrate is imaged by first uniformly electrostatically charging the surface of the photoconductive layer, and then exposing the charged surface to a pattern of light. The light exposure selectively dissipates the charge in the illuminated areas, thereby forming a pattern of charged and uncharged areas. A liquid or solid toner is then deposited in either the charged or uncharged areas depending on the properties of the toner to create a toner image on the surface of the photoconductive layer. The resulting toner image can be transferred to a suitable receiving surface such as paper. The imaging process can be repeated many times to complete a single image and/or to reproduce additional images.
Both single layer and multilayer photoconductive elements have been used. In single layer embodiments, a charge transport material and charge generating material are combined with a polymeric binder and then deposited on the electrically conductive substrate. In multilayer embodiments, the charge transport material and charge generating material are in the form of separate layers, each of which can optionally be combined with a polymeric binder, deposited on the electrically conductive substrate. Two arrangements are possible. In one arrangement (the xe2x80x9cdual layerxe2x80x9d arrangement), the charge generating layer is deposited on the electrically conductive substrate and the charge transport layer is deposited on top of the charge generating layer. In an alternate arrangement (the xe2x80x9cinverted dual layerxe2x80x9d arrangement), the order of the charge transport layer and charge generating layer is reversed.
In both the single and multilayer photoconductive elements, the purpose of the charge generating material is to generate charge carriers (i.e., holes and/or electrons) upon exposure to light. The purpose of the charge transport compound is to accept at least one type of these charge carriers, generally holes, and transport them through the charge transport layer in order to facilitate discharge of a surface charge on the photoconductive element.
In a first aspect, the invention features an organophotoreceptor that includes:
(a) a charge transport compound having the formula 
where R1 has a structure of: 
in which Ar is selected form the group consisting of; 
R4 is a hydrogen or an aromatic group and R2 and R3 are, independently, an (N,N-disubstituted) arylamine group;
(b) a charge generating compound; and
(c) an electrically conductive substrate over which the charge transport compound and the charge generating compound are located.
In a second aspect, the invention features an electrophotographic imaging apparatus that includes (a) a plurality of support rollers; and (b) the above-described organophotoreceptor operably coupled to the support rollers with motion of the support rollers resulting in motion of the organophotoreceptor. The apparatus can further comprise a liquid or solid toner dispenser.
In a third aspect, the invention features an electrophotographic imaging process that includes (a) applying an electrical charge to a surface of the above-described organophotoreceptor; (b) imagewise exposing the surface of the organophotoreceptor to radiation to dissipate charge in selected areas and thereby form a pattern of charged and uncharged areas on the surface; (c) contacting the surface with a liquid or dry toner to create a toned image; and (d) transferring the toned image to a substrate.
In a fourth aspect, the invention features an improved charge transport compound having the formula 
where R1 has a structure of: 
in which Ar is selected form the group consisting of; 
R4 is a hydrogen or an aromatic group and R2 and R3 are, independently, an (N,N-disubstituted) arylamine group.
In another aspect, the invention features a charge transport compound having the formula 
where R1 has a structure of 
and R2 is a julolidene group or a carbazole group. These charge transport compounds can further be used in the formation of organophotoreceptors as well as corresponding electrophotographic imaging apparatuses and electrophotographic imaging processes.
These photoreceptors can be used successfully with liquid toners to produce high quality images. The high quality of the images can be maintained after repeated cycling.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims.